This invention relates to burnishing heads for burnishing magnetic disks and methods for burnishing magnetic disks.
Magnetic disks are typically manufactured with the following method:    1. An aluminum alloy substrate is electroless plated with a nickel-phosphorus alloy.    2. The plated substrate is textured.    3. One or more underlayers, one or more magnetic layers, and one or more protective overcoats are deposited on the plated, textured substrate. (It is also known to deposit other layers onto the substrate as well.)    4. A lubricant is applied to the protective overcoat.    5. The resulting disk is then burnished.
During burnishing, the disk is rotated, and a burnishing head flies over the disk to remove undesired contaminant particles. Such contaminant particles can comprise Al2O3 generated during a “kiss-buff” process or an edge buff process. Enhancing particle removal efficiency during burnishing is an important process objective. FIG. 1 illustrates a prior art burnishing head 10 burnishing a magnetic disk 12. Head 10 is held by a suspension 14 while disk 12 rotates in a direction 16. Head 10 is held at an angle α of about 15° relative to the motion of travel of disk 12. During burnishing, head 10 removes contaminant particles from the surface of disk 12.
FIGS. 2A, 2B and 2C illustrate side, rear and bottom views of head 10. As can be seen, head 10 comprises first and second rails 18a, 18b extending from a bottom surface of head 10. Rails 18a, 18b are parallel to a central axis C of head 10, and comprise an inclined portion or ramp 20 that assists head 10 to “fly” above disk 12. Rails 18a, 18b have a height H1 of about 100 μm, and are formed by a mechanical machining process. Rails 18a, 18b have side walls 22 that are substantially vertical with respect to the body of head 10, and have a sharp rail corner. (By rail corner we mean the corner where rail side walls 22 meet rail air bearing surface 24.)
It is also known that burnish heads have been made with etching process. Rails formed by etching have a height of about 5 to 10 μm. (It would take a long time to etch rails of substantially greater height.) Some prior art burnishing heads formed by etching have rounded rail corners and some prior art heads formed by etching have fairly sharp rail corners. Also, some prior art burnishing head rails formed by etching have side walls at an angle, e.g. about 60° with respect to the horizontal, whereas other prior art burnishing head rails formed by etching have side walls close to vertical. However, to the best of our knowledge, the etching process conditions used to form prior art rails that have vertical walls when the rails are only about 10 μm high, would result in sloped walls if used to form rails that were much higher, e.g. 75 μm high.
(Although burnishing head 10 comprises a pair of rails, it is also known in the art to provide burnishing heads having burnishing surfaces such as those shown in U.S. Pat. No. 4,845,816, issued to Nanis, U.S. Pat. No. 6,267,645, issued to Burga, and U.S. Patent Application publication US 2002/0029448A1.)
Burnishing heads differ in structure and function from read-write heads. An example of a read-write head is discussed in U.S. Pat. No. 5,949,614, issued to Chhabra. A read-write head is incorporated into a disk drive. Such a head flies over a magnetic disk during use. A transducer provided at the trailing end of the read-write head reads data from and writes data to the disk. Burnishing heads typically lack such transducers.
Another type of head is used to detect asperities on a magnetic disk surface. Such a head comprises a sensor for sensing mechanical impact of the head against asperities. Burnishing heads typically lack transducers of this type as well. Such heads are discussed in by Burga et al. in U.S. Pat. Nos. 5,963,396 and 6,138,502.
Unfortunately, from time to time, burnishing head 10 may contact disk 10 during burnishing and stay in the avalanche mode. It takes time for head 10 to “recover” from such contact, resume flight over the surface of disk 10, and thereafter resume burnishing disk 10. It would be desirable to reduce the amount of time required for head 10 to recover. Also, the burnishing head 10 shows unstable flying characteristics near the outer edge of the disk 10 since the slider body is not parallel to the direction of the air flow under ABS. This is undesirable for burnishing operation because unstable flying of the head could result in head-disk interaction causing defect generation on the disk. It would be desirable to improve these aspects of burnishing heads.